Preheat the oven to 425°. Spray an 8-inch or 9-inch round pan with a light coat of cooking spray and set aside.
Place flour in a large bowl. Use a pastry cutter or forks to work the butter into the flour until the lumps are about the size of large peas. Alternatively, you can freeze the butter and use a grater to grate the butter into the flour.
Add ⅔ cup of buttermilk, and use a wooden spoon or spatula to stir until a soft dough forms. Add small amounts of additional buttermilk slowly, as needed, until the dough reaches this consistency.
Flour a work surface. Turn out onto a lightly floured surface and knead for about 1 minute (folding the dough back over on itself), adding flour to the counter and your hands, as necessary, to prevent sticking. Pat to ¾-inch thickness.
Use a biscuit cutter to cut out the individual biscuits. I used a 2 ½ -inch cutter here, which yielded 7-8 large biscuits. You can also use a 2-inch cutter to yield about 12 biscuits. Firmly press the cutter down into the dough, but do not twist. Twisting the biscuit cutter seals off the edges of the biscuits and they therefore will not rise as high.
Roll out the dough once or twice more to use up the remaining dough scraps.
Arrange the biscuits in the prepared pan so that their sides are touching.
At this point, the dough will be a bit warmer from working with it, so I like to place the pan of biscuits in the refrigerator or freezer for 5-10 minutes to chill again (but do not leave it in the fridge or freezer any longer than that).
Just before you put the biscuits in the oven, brush the tops with melted butter.
Bake for 14 -15 minutes, or until they're a light golden brown. Brush the tops of the biscuits with additional melted butter when they come out of the oven and serve warm.